What's the different between JWSDP and JSWDK?

Is the JWSDP a higher version of JSWDK? It includes Tomcat, but why I can't compile a servlet under it. I set the classpath=C:\jwsdp-1_0\common\lib\servlet.jar;C:\jwsdp-1_0\common\lib\jasper-compiler.jar;. After I restart my WinXp(home edition) and compile the sample HelloWorld.java(servlet) I get compile errors: package javax.Servlet does not exist. What's wrong? Could you help me to fix this problem? Thanx!